1. Field of the Invention
The invention relates to detecting and correcting errors in arrays after successful ABIST testing, where diagnostic testing is performed upon the array after ABIST testing, and the detected error or fault is isolated.
2. Background Art
The problem of past s390-processors was, that whenever a PU (processor unit) has an array with errors found by abist-tests, there was no possibility to disable part or all of this array. In this cases the PU couldn't be used at all since the abist-tests didn't pass IML.
Especially the sensitive PCAMs used in Bluefire did often fail and decrease the yield heavily, and therefore we looked for a solution to get also PUs with defect array sets running.
Because the yield-problem will most likely get bigger with new technologies and having more cores on a chip, it might be useful to have also partial good chips with failing arrays for spare PUs or at least for chip and system bring-up.
Actually array fails occurring during normal operation mode (after abist-tests did run successfully) leads in deletion of the failing array set. This ensures, that the PU can be used also after an upcoming fail, but with less array sets (results in slightly decreased performance, but w/o showing functional problems). The problem is, that PUs with defective arrays found on the tester cannot be used in a system.
Because of the given performance delta it also implies that such a processor can not be shipped the same as a processor without any array sets disabled for the performance delta between the two is readily measurable.